Having been issued and worn FRACUs as an Army firefighter, and worn both kinds of wildland pants you can get from GSA, what you're seeking is the Type II Ripstop wildland pant. The more you wash them, the softer they get, and theyre fucking bombproof. The velcro on the cargos and cuffs will wear out before the pants themselves do (and are easily replaced). Unlike the Type I pants which are the cheap, ill fitting, semi-durable, dark green ones every swinging dick gets issued.
Plus no safety officer will ever have a hard-on for them.
Here is an NSN list by size:
The FRACUs were plenty comfortable, but very thin, and not what I would pack in my red bag if I had the option.